My TP-Link TL-WR843ND is seemingly limited to 15 concurrent usert (MAC addresses). After that it simply refuses anothe connection
My TD-W8961ND seems to be limited to 8 wireless connections. Note that my DHCP settings have an IP pool count of 100, that is not the bottleneck on my router.
None of the router manufactures mention exact number of device that can connect the wireless router. But there may be limited number of device can connect and its almost depends on the network bandwidth. Think this might be the reason manufacturers not specify number of device which can connect and its also depends on many factors.
@Rory WiFi connection and speed is mainly depends on bandwidth availability. On a typical decent router the number of DHCP address will be limited by the allowance made by the subnet mask, which is usually a /24 allowance, so 255.255.255.0. This automatically limits the number of DHCP clients to 255, but one IP address is always taken by the router so 254 is the max you will get on most routers.
In case if the DHCP ip's are allotted to printers or systems in LAN then you will face reduction in 254 count.
I checked that website you gave and noticed that it has 4 Guest WiFi SSIDs it means each can set up to 16 at an average it means your modem can handle 64 client request with out any issues theoretically.
Note : Just call the customer care of that product and get the benchmark values what they got for their product in testing lab.
The WiFi chip in an access point has to hold the MAC address of each connected device. In budget chips there is only space for 8 MAC addresses. If you can find out what chip is in a device, you can find out the maximum number of MAC addresses. For example, an RTL8051 can handle only 8 MAC addresses.